Controllable synthesis, optical and photocatalytic properties of CuS nanomaterials with hierarchical structures

A high performance fiber-optic sensor for Cu2+ ions is proposed based on monodispersed hydrophobic CdSe/ZnS nanoparticles encapsulated within a silica shell and immobilized on the tip of an optical fiber by a polyvinyl alcohol (PVA) polymer coating. The experimental results show that the core–shell CdSe/ZnS@SiO2 nanostructure exhibits a strong reduction in luminescence intensity following interaction with Cu2+ ions. The porous silica shell of the nanostructure also plays a key role in the fluorescence quenching process by preventing the aggregation of the CdSe/ZnS nanoparticles; thereby promoting the adsorption of the Cu2+ ions. There were linear relationships between the relative fluorescence intensity (I0/I) and the concentration for Cu2+ ions from 0 to 10 μM (R2 = 0.9858). The resolution of this sensor detected by a commercial hand-held spectrometer was about 0.9 μM and therefore it is an ideal solution for applications in chemical and medical detections. The use of a silica-coated CdSe/ZnS QD has a number of key advantages as compared to the organic ligand modified QDs, including better selectivity, higher sensitivity, better chemical stability, and more stable with wide pH value.

Highly sensitive and selective sensor based on silica-coated CdSe/ZnS nanoparticles for Cu2+ ion detection

The usual high temperature wurtzite phase of ZnS was successfully obtained at low temperature (170 °C) in the presence of ethylenediamine (EN) as the soft template. X-ray diffraction and Raman spectroscopy analysis confirmed the EN-mediated phase transformation (zinc blende to wurtzite) of ZnS. X-ray photoelectron spectroscopy (XPS) showed that all the samples were sulfur deficient. A high temperature X-ray diffraction (XRD) study showed that ZnS samples, both EN-mediated and without EN, retained their phases except small changes in the unit cell dimension. Besides the EN-mediated phase transition, morphology transformations from nearly spherical shape to nanorods are also observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The coupling between EN molecules with ZnS is confirmed by Fourier transform infrared spectroscopy. A significant reduction in the phase transition temperature of ZnS has been achieved as compared to the bulk transition temperature (1020 °C). Mech...

Ethylenediamine-Mediated Wurtzite Phase Formation in ZnS

Although nanozinc oxide (nano-ZnO) is applied widely in photocatalysts and gas sensors and in biological fields, it can cause serious oxidative stress and DNA damage to mammalian cells. Our aim in this study was to reduce the cytotoxicity of nano-ZnO by coating it with a TiO2 layer. We used a sol−gel method to synthesize core (nano-ZnO)/shell (TiO2) nanoparticles (NPs) with various degrees of coating. Transmission electron microscopy and Raman spectroscopy confirmed that TiO2 was coated on the nano-ZnO. Moreover, a decrease in the intensity of the pre-edge signal in Ti K-edge X-ray absorption near edge structure spectra revealed that the core/shell NPs had more Ti−O coordination than pure TiO2 particles; in addition, the Zn K-edge extended X-ray absorption fine structure spectra revealed that after the ZnO NPs had been coated with TiO2, the coordination number of the ZnO shell increased to 3.3 but that of the ZnZn shell decreased to 6.2, providing further evidence for the ZnO/TiO2 core/shell structure. To...

/pdf/titanium-oxide-shell-coatings-decrease-the-cytotoxicity-of-4bqyh4oks2.pdf

Titanium oxide shell coatings decrease the cytotoxicity of ZnO nanoparticles.

By sequential growth of the core and shell of different materials, ZnO/ZnS and ZnO/MgO core/shell nanowire arrays are fabricated. Photoluminescence properties of these samples with different shell thicknesses are studied in detail. The results indicate that the ZnS shell thickness as a function of treatment time will noticeably change the photoluminescence intensity of the ZnO nanowires, whereas the MgO shell will not change the photoluminescence intensity any more after it saturates the surface dangling bonds of ZnO core. Large-scale first-principles calculations indicate that, unlike the ZnO/MgO core/shell nanowires, the electrons and holes of which are both confined in the core of the nanowires (type-I heterostructures), the ZnO/ZnS core/shell nanowires are type-II heterostructures, the electrons and holes of which are respectively confined in the core and the shell; as a result, the separation of electrons and holes in the ZnO/ZnS core/shell nanowires will reduce the spatial overlap between them, lead...

Yin Jiang

Papers

Structural and luminescent properties of ZnO nanorods and ZnO/ZnS nanocomposites

Synthesis and characterization of ZnO/SiO2 core/shell nanocomposites and hollow SiO2 nanostructures